Processes for the carbonylation of olefinically unsaturated hydrocarbons are known from British Patent Specification No. 1,110,405 and from U.S. Pat. Nos. 4,172,087 and 4,414,409 inter alia.
In the British Patent Specification No. 1,110,405 published Apr. 18, 1968, a process is described for the preparation of esters by the reaction of a diene with carbon monoxide and an alcohol or phenol in the presence of a catalyst containing platinum and/or palladium and/or nickel, and/either
(a) bromide and/or iodide ions or
(b)
(i) a ligand that is able to form a coordination linkage with the metal component of the catalyst and that contains nitrogen, phosphorus, arsenic or sulfur, preference being given to trivalent phosphorus-containing ligands, and particular preference to a primary, secondary or tertiary phosphine or an alkyl, aryl or cycloalkyl phosphite and PA1 (ii) chloride, bromide or iodide. PA1 (i) at least a catalytic quantity of a palladium catalyst consisting of either one or more palladium halides in combination with one or more tertiary-phosphorus-containing monodentate donor ligands or one or more halide-free palladium salts in combination with one or more tertiary-phosphorus-containing multidentate donor ligands. PA1 (ii) at least one molar equivalent of a hydroxyl-group-containing co-reactant selected from the group consisting of water or an aliphatic alcohol containing 1 to 12 carbon atoms, and PA1 (iii) an (N-heterocyclic) amine base;
Although the conversion of butadiene is mentioned as one of the embodiments, preference is clearly given on page 2, lines 97-103, to dienes as starting compounds, wherein the double bonds are separated by 2, 3 or 4 single bonds. Moreover, the presence of bromide, iodide or chloride is considered to be essential. The reaction is preferred slightly to be performed in an acidified reaction medium by, for example, the presence of toluenesulfonic acid therein.
From the yields of pent-3-enoate obtained in the relevant examples, it will be clear to a person skilled in the art that the aforesaid British patent specification certainly does not provide this expert with any indications for the very selective preparation of pent-3-enoate and higher homologues from 1,3-butadiene and higher conjugated dienes.
From U.S. Pat. No. 4,172,087, issued Oct. 13, 1979, a process is known for the simultaneous preparation of two groups of unsaturated carboxylic acids and esters thereof from aliphatically conjugated diene starting materials containing from 4 to 8 carbon atoms, wherein:
(a) every two moles of the aliphatically conjugated diene concerned are mixed with a three-component mixture consisting of
(b) the reaction mixture is pressurized with sufficient carbon monoxide to satisfy the stoichiometry of the carbonylation reaction;
(c) the pressurized reaction mixture is heated until substantial formation of the desired aliphatic carboxylic acid derivatives has been achieved; and
(d) the unsaturated carboxylic acid derivatives concerned that occur therein are isolated.
Although the conversion of 1,3-butadiene and aliphatically conjugated diene is mentioned, the presence of an N-heterocyclic base, such as pyridine, alkylated pyridines, quinoline, lutidine, picoline, isoquinoline, alkylated quinolines and isoquinolines, acridine and N-methyl-2-pyrrolidone or N,N-dimethylaniline, N,N-diethylaniline, N,N-diethyltoluidine, N,N-dibutyl-toluidine and N,N-dimethylformamide, is considered to be an essential precondition.
In particular, from the yields of pent-3-enoate mentioned in the described examples, it will be clear to an expert that the process according to the aforesaid U.S. Pat. No. 4,172,087 certainly gives no indications for a very selective preparation of pent-3-enoate and higher homologues from 1,3-butadiene and higher conjugated dienes.
From the U.S. Pat. No. 4,414,409, issued Nov. 8, 1983, a carbonylation process is known for the preparation of acids and esters by conversion of an olefinically unsaturated compound, carbon monoxide and a hydroxyl compound at about 50.degree. C. to about 150.degree. C., in the presence of a catalyst consisting of an organic phosphine ligand palladium complex and a perfluorosulfonic acid.
A clear preference is, moreover, indicated in column 2, lines 26-29, and in column 9, line 27, for the conversion of non-conjugated hydrocarbons.
It will be clear that the processes described hereinbefore are either unsuitable for the conversion of conjugated unsaturated compounds or, in particular, do not seem to be suited to a very selective preparation of 3-pentenoic acid or derivatives and higher homologues, and that those skilled in the art, searching for improved selective preparation methods for 3-pentenoic acid and derivatives thereof, which are becoming an increasingly important starting material for organic syntheses (for example, for the preparation of adipic acid and derivatives thereof), have been diverted away from the methods described hereinbefore.
More in general, a number of known processes have the disadvantage that they use relatively high concentrations of the relevant catalyst system and also use aggressive reaction components, for example, acids such as hydrohalogenic acids or salts thereof and other rigorous reaction conditions, which necessitate cost-increasing measures in connection with safety and the apparatus life (corrosion).
An object of the present invention, therefore, is to provide an improved very selective carbonylation of 1,3-butadiene and higher homologues to very valuable products, such as 3-pentenoic acid or derivatives thereof.
Another object of the present invention is to provide a novel catalytic system for said carbonylation process formed by combining a palladium compound with bidentate phosphine(s).